The unit, known as Alec Station, was disbanded late last year and its analysts reassigned within the C.I.A. Counterterrorist Center, the officials said.

The decision is a milestone for the agency, which formed the unit before Osama bin Laden became a household name and bolstered its ranks after the Sept. 11 attacks, when President Bush pledged to bring Mr. bin Laden to justice "dead or alive."

The realignment reflects a view that Al Qaeda is no longer as hierarchical as it once was, intelligence officials said, and a growing concern about Qaeda-inspired groups that have begun carrying out attacks independent of Mr. bin Laden and his top deputy, Ayman al-Zawahiri.

Agency officials said that tracking Mr. bin Laden and his deputies remained a high priority, and that the decision to disband the unit was not a sign that the effort had slackened. Instead, the officials said, it reflects a belief that the agency can better deal with high-level threats by focusing on regional trends rather than on specific organizations or individuals.

"The efforts to find Osama bin Laden are as strong as ever," said Jennifer Millerwise Dyck, a C.I.A. spokeswoman. "This is an agile agency, and the decision was made to ensure greater reach and focus."

Michael Scheuer, a former senior C.I.A. official who was the first head of the unit, said the move reflected a view within the agency that Mr. bin Laden was no longer the threat he once was.

Mr. Scheuer said that view was mistaken.

"This will clearly denigrate our operations against Al Qaeda," he said. "These days at the agency, bin Laden and Al Qaeda appear to be treated merely as first among equals."

In recent years, the war in Iraq has stretched the resources of the intelligence agencies and the Pentagon, generating new priorities for American officials. For instance, much of the military's counterterrorism units, like the Army's Delta Force, had been redirected from the hunt for Mr. bin Laden to the search for Abu Musab al-Zarqawi, who was killed last month in Iraq.

An intelligence official who was granted anonymity to discuss classified information said the closing of the bin Laden unit reflected a greater grasp of the organization. "Our understanding of Al Qaeda has greatly evolved from where it was in the late 1990's," the official said, but added, "There are still people who wake up every day with the job of trying to find bin Laden."

Established in 1996, when Mr. bin Laden's calls for global jihad were a source of increasing concern for officials in Washington, Alec Station operated in a similar fashion to that of other agency stations around the globe.

The two dozen staff members who worked at the station, which was named after Mr. Scheuer's son and was housed in leased offices near agency headquarters in northern Virginia, issued regular cables to the agency about Mr. bin Laden's growing abilities and his desire to strike American targets throughout the world.

In his book "Ghost Wars," which chronicles the agency's efforts to hunt Mr. bin Laden in the years before the Sept. 11 attacks, Steve Coll wrote that some inside the agency likened Alec Station to a cult that became obsessed with Al Qaeda.

"The bin Laden unit's analysts were so intense about their work that they made some of their C.I.A. colleagues uncomfortable," Mr. Coll wrote. Members of Alec Station "called themselves 'the Manson Family' because they had acquired a reputation for crazed alarmism about the rising Al Qaeda threat."

Intelligence officials said Alec Station was disbanded after Robert Grenier, who until February was in charge of the Counterterrorist Center, decided the agency needed to reorganize to better address constant changes in terrorist organizations.